Corrosion mechanism and performance of Cr-coated Zr-4 alloy in 360 °C water and 1300 °C steam

A dense and uniform Cr coating is prepared on the Zr-4 alloy using multi-arc ion plating technology, with the aim of serving as an accident-tolerant fuel cladding for light water reactors. The corrosion performance of Cr-coated Zr-4 alloy is investigated after exposure to 360 °C and 18.6 MPa corrosion conditions for up to 5040 h, and its corrosion mechanism is discussed. Furthermore, the oxidation behavior of the Cr-coated Zr-4 alloy in steam at 1300 °C is mainly examined. It is observed that the ZrO2 channel within the Cr coating acts as an oxygen diffusion path during steam oxidation and facilitates the reduction of Cr2O3 by providing Zr. When the ZrO2 channel diffuses to the Cr2O3/Cr interface, Cr2O3 is reduced to form ZrO2 and Cr. When the thickness of the Cr2O3 layer is minimized, the Cr coating fails. The in-situ oxidation of the Cr2Zr layer results in the formation of ZrO2 and Cr2O3, while the substrate beneath the Cr coating is oxidized to form a ZrO2 layer. The whole oxidation process of the Cr-coated Zr-4 alloy up to 1300 °C is presented in detail.